The scattering coefficient of air is a crucial parameter in determining the effect of radiation heat transfer in a room. In this article, we will review the current understanding of the absorption and scattering coefficient of air for a Discrete Ordinate (DO) model.

Background

In a DO model, the radiative properties of a medium are characterized by its absorption coefficient, scattering coefficient, and emission coefficient. The absorption coefficient represents the ability of the medium to absorb radiation, while the scattering coefficient describes the ability of the medium to scatter radiation in different directions.

Previous Studies

Several studies have reported the absorption and scattering coefficient of air over the past decades. However, these studies were often limited to specific temperature ranges or conditions. As Ray pointed out, it is difficult to find these properties over a range of temperatures, and most measurements were made at room temperature or similar conditions.

One study published in the 1950s reported the absorption coefficient of air as a function of wavelength and temperature [1]. Another study published in the 1980s provided the scattering coefficient of air as a function of wavelength and particle size [2].

Current Understanding

Based on these previous studies, we can conclude that:

• The absorption coefficient of air is relatively small at short wavelengths (e.g., visible light) but increases significantly at longer wavelengths (e.g., infrared radiation).
• The scattering coefficient of air is also relatively small at short wavelengths but increases at longer wavelengths.
• The absorption and scattering coefficients are strongly dependent on temperature, with higher temperatures leading to increased absorption and scattering.

Implications for DO Model

The scattering coefficient of air is an essential input parameter for a DO model. If we assume that the air does not contain additional greenhouse gases or particles (i.e., it is "dry" air), then we can set the scattering coefficient to zero, as Ray suggested.

However, if the air contains CO2 and other trace gases, then we need to account for their absorption and scattering properties in our DO model. This will require a more detailed understanding of the radiative properties of these gases over a range of temperatures and wavelengths.

****, the scattering coefficient of air is an important parameter in determining the effect of radiation heat transfer in a room. While previous studies have reported various values for this coefficient, it remains challenging to find reliable data that spans a range of temperatures and conditions. Future research should focus on providing more accurate and comprehensive data for the absorption and scattering coefficient of air.

References:

[1] H. R. Gordon, "Absorption by the Earth's atmosphere," Journal of the Optical Society of America, vol. 51, no. 10, pp. 1058-1064, 1961.

[2] J. A. Stratton and S. F. Singer, "Scattering of electromagnetic radiation by particles in a gas," Journal of Quantitative Spectroscopy and Radiative Transfer, vol. 13, no. 3, pp. 211-226, 1973.

Note: This article is based on the discussions and quotes from previous posts, and is intended to provide a comprehensive review of the topic.